Facebook is facing a hefty fine after the city of Seattle, in Washington, accused the social media giant of violating its political ad transparency law.

According to the claims, Facebook violated the state's 1977 campaign finance law, which states that those who accept advertising dollars from political campaigns be transparent with the public about the "exact nature and extent of the advertising services".

News portal Fast Company reported that if Facebook is found at fault, it could be liable for $5,000 per violation.

Under state law, advertisers who provide political advertising during a campaign must make available the names and addresses of the people it accepted the ads from, the exact nature and extent of the advertising and the "consideration and the manner of paying".

"Though the law was initially enacted in 1977, it is interpreted to apply to all forms of advertisements, including print, television, radio and Internet," the report pointed out.

In December, a Seattle newspaper, The Stranger, requested 2017 state election ad data from Facebook.

On failure to get a satisfactory response, Wayne Barnett, Executive Director of the Seattle Ethics and Elections Commission, sent Facebook a letter giving the company until January 2 to comply with the request.

At that time, Facebook requested a 30-day extension, which was granted.

Last Friday, the social media giant served a two-page spreadsheet which Barnett said fell short of providing the information required by law.

The document lists candidate names, their Facebook page names, Facebook page addresses, total spend, service provided and manner of payment.

"The problem is that a lot of the information Facebook provided seems limited and it does not match with the disclosure filings from the candidates themselves," the report said.

The Stranger claimed that the possible reason for the mismatched numbers was that many of those Facebook ads were purchased through third parties, like political consultants, and not directly through the candidates' own Facebook pages.